The objectives of the proposed research are to determine the intracellular location of several constituents and the route of translocation of calcium, phosphorus and other elements in bone cells during bone formation and resorption. The methodology for these studies is critical and consists of electron microprobe analysis of bone prepared by ultracryomicrotomy. Autoradiography and immunohistochemical procedures will be used for detecting carbonic anhydrase at the electron microscope level in osteoclasts and other tissues. The influence of parathyroid hormone and calcitonin on carbonic anhydrase levels in osteoclasts will be assessed.